Re: [PATCH RESEND] lib/group_cpus: make group CPU cluster aware

Guo, Wangyang
2025-11-18T06:29:41Z

On 11/13/2025 9:38 AM, Ming Lei wrote:
> On Wed, Nov 12, 2025 at 11:02:47AM +0800, Guo, Wangyang wrote:
>> On 11/11/2025 8:08 PM, Ming Lei wrote:
>>> On Tue, Nov 11, 2025 at 01:31:04PM +0800, Guo, Wangyang wrote:
>>> They still should share same L3 cache, and cpus_share_cache() should be
>>> true when the IO completes on the CPU which belong to different L2 with the
>>> submission CPU, and remote completion via IPI won't be triggered.
>> Yes, remote IPI not triggered.
>
> OK, in my test on AMD zen4, NVMe performance can be dropped to 1/2 - 1/3 if
> remote IPI is triggered in case of crossing L3, which is understandable.
>
> I will check if topo cluster can cover L3, if yes, the patch still can be
> simplified a lot by introducing sub-node spread by changing build_node_to_cpumask()
> and adding nr_sub_nodes.

Do you mean using cluster as "NUMA" nodes to spread CPU, instead of two
level NUMA-cluster spreading?

BR
Wangyang